The present invention generally relates to a trip latch for use with high current switches for circuit breakers, and more particularly relates to a trip latch having a primary and a secondary trip shaft for reducing the load required for opening.
Switches are used in circuit breakers and switchboards to disconnect and distribute power for commercial and industrial applications. During operation, the need often arises to trip the switches to prevent, explosions, fires or potential damage to downstream equipment. Typically, the switches are fitted with trip latches that cause the switch to trip and open under a predetermined load generated by a current signal.
High current switches typically require large operating forces to insure opening under the predetermined load. Trip latches in such high current switches may require loads of between 20 to 25 pounds to reliably trip the switches. Among the problems presented by generating loads of this magnitude is having to provide larger transformers having larger solenoids. Accordingly, there is a need for an effective and efficient means to reduce the loads necessary to trip high current switches.
The present invention is provided to solve these and other problems and to provide other advantages. A preferred embodiment will be disclosed, and the novel aspects of the present invention will be particularly identified and discussed herein.
It is an object of the present invention to provide a two-stage trip latch for high current switches and circuit breakers.
According to the present invention, the trip latch having an open position and reset-stop position is disposed within a switch housing. The trip latch has a force member for providing a force to a primary trip shaft. The primary trip shaft has a first end rotatably connected at opposed first and second ends in the front and rear frame, and a reductor arm extending therefrom. The trip latch further includes a secondary trip shaft rotatably connected at opposed ends to the front and rear frames of the housing proximate and substantially parallel to the primary trip shalt such that the reductor arm engages a bottom portion of the secondary trip shaft. The secondary trip shaft is shaped such that when the secondary trip shaft is rotated the reductor arm may rotate past the secondary trip shaft, thereby causing the trip latch to open.
According to another aspect of the invention, the force member is a rotatable opening crank, wherein the opening crank has a first end and a second end. The first end is attached to a compressible spring to provide a rotating force and the second end of the opening crank has a latch step for engaging the primary trip shaft.
According to another aspect of the invention, the force member is a linear moving member having a first and second end. Again, the first end is attached to a compressible spring to provide a force and the second end engages the primary trip shaft.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.